MicroRNAs (miRNAs)
play an important role in the regulation of
gene expression. They play a regulatory role in various nutrient assimilatory
pathways of plants; however, their role in the regulation of sulfur
uptake and assimilatory pathways in mustard cultivars under high/low
sulfur conditions is not elucidated. Sulfur is essential for plant
growth and development, and its deficiency can cause a decline in
oil seed content and thus lower the economic yield in
Brassica
juncea
. In this study, different miRNAs involved in the regulation
of sulfur uptake and assimilation pathways in
B. juncea
were identified using a psRNA target analyzer and miRanda database
tools. The predicted miRNAs that belong to 10 highly conserved families
were validated using stem-loop RT-PCR. The
B. juncea
cultivars Pusa Jaikisan, Pusa Bold, and Varuna were kept in sulfur-excessive
(high) and -deficient (insufficient) conditions, and expression studies
of miRNAs and their target mRNAs were carried out using qRT-PCR. The
correlation between the expression pattern of miRNAs and their target
genes showed their potential role in sulfur uptake and assimilation.
Analysis with 5′ RACE revealed the authentic target of miRNAs.
The influence of S treatments on metabolites and sulfur content was
also studied using GC-MS and a CHNS analyzer. Our study showed the
potential role of miRNAs in the regulation of sulfur uptake and assimilation
and put forward the implications of these molecules to enhance the
sulfur content of
B. juncea.
With the advent of modern lifestyles, diabetes-related
comorbidities
attributed the importance of low-caloric natural sweetener plants
such as
Stevia rebaudiana
. This plant
is the viable source of steviol glycosides (SGs) and other economically
important secondary metabolites. Glandular trichomes (GTs) play the
role as a reservoir for all secondary products present in the plant
species. Therefore, the present study was carried out to evaluate
the influence of different plant growth regulators (PGRs) on GT density
and its impact on the SG content. The direct shoot regeneration system
was developed on Murashige and Skoog (MS) + benzyl aminopurine (BAP)
(1.0 mg/L) + naphthaleneacetic acid (NAA) (0.5 mg/L), and MS + BAP
(1.5 mg/L) + NAA (0.5 mg/L) from nodal and leaf explants, respectively.
Among the combination of PGRs used, MS medium fortified with BAP (1.0
mg/L) and 2,4-dichlorophenoxyacetic acid (2,4-D) (0.5 mg/L) played
a significant role in increasing the GT density on leaf and stem tissues
of
S. rebaudiana
. Furthermore, high-performance
thin-layer chromatography and gas chromatography–mass spectrophotometry
data confirmed a notable rise in SGs and other valuable secondary
metabolites. Thus, the protocol developed can be used for the propagation
of stevia with an improved metabolic profile at a large scale.
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